SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f98e4d48dc16b606d553896399a3a7fa94d5989eae1c94ddd2bee286dfceed26' 
  AND token = 'FatnvAFrm+McPlOnAWlW2HbpOqiUPQnMzSpcyg/3EYU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}